Update SDL2 to newest version to fix 7.1 playback

This fixes 7.1 playback. Before this commit, SDL used 7.1 front audio configuration with Center Left and Center Right speakers, but without Rear speakers.

See https://github.com/libsdl-org/SDL/issues/11709 for more details.

libs/SDL2/include/SDL_test_font.h

@@ -1,6 +1,6 @@
 /*
   Simple DirectMedia Layer
-  Copyright (C) 1997-2023 Sam Lantinga <slouken@libsdl.org>
+  Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.org>
 
   This software is provided 'as-is', without any express or implied
   warranty.  In no event will the authors be held liable for any damages
@@ -19,7 +19,7 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 
-/**
+/*
  *  \file SDL_test_font.h
  *
  *  Include file for SDL test framework.
@@ -41,7 +41,7 @@ extern "C" {
 #define FONT_CHARACTER_SIZE 8
 #define FONT_LINE_HEIGHT    (FONT_CHARACTER_SIZE + 2)
 
-/**
+/*
  *  \brief Draw a string in the currently set font.
  *
  *  \param renderer The renderer to draw on.
@@ -53,7 +53,7 @@ extern "C" {
  */
 int SDLTest_DrawCharacter(SDL_Renderer *renderer, int x, int y, Uint32 c);
 
-/**
+/*
  *  \brief Draw a UTF-8 string in the currently set font.
  *
  *  The font currently only supports characters in the Basic Latin and Latin-1 Supplement sets.
@@ -67,7 +67,7 @@ int SDLTest_DrawCharacter(SDL_Renderer *renderer, int x, int y, Uint32 c);
  */
 int SDLTest_DrawString(SDL_Renderer *renderer, int x, int y, const char *s);
 
-/**
+/*
  *  \brief Data used for multi-line text output
  */
 typedef struct SDLTest_TextWindow
@@ -78,7 +78,7 @@ typedef struct SDLTest_TextWindow
     char **lines;
 } SDLTest_TextWindow;
 
-/**
+/*
  *  \brief Create a multi-line text output window
  *
  *  \param x The X coordinate of the upper left corner of the window.
@@ -92,7 +92,7 @@ typedef struct SDLTest_TextWindow
  */
 SDLTest_TextWindow *SDLTest_TextWindowCreate(int x, int y, int w, int h);
 
-/**
+/*
  *  \brief Display a multi-line text output window
  *
  *  This function should be called every frame to display the text
@@ -104,7 +104,7 @@ SDLTest_TextWindow *SDLTest_TextWindowCreate(int x, int y, int w, int h);
  */
 void SDLTest_TextWindowDisplay(SDLTest_TextWindow *textwin, SDL_Renderer *renderer);
 
-/**
+/*
  *  \brief Add text to a multi-line text output window
  *
  *  Adds UTF-8 text to the end of the current text. The newline character starts a
@@ -119,7 +119,7 @@ void SDLTest_TextWindowDisplay(SDLTest_TextWindow *textwin, SDL_Renderer *render
  */
 void SDLTest_TextWindowAddText(SDLTest_TextWindow *textwin, SDL_PRINTF_FORMAT_STRING const char *fmt, ...) SDL_PRINTF_VARARG_FUNC(2);
 
-/**
+/*
  *  \brief Add text to a multi-line text output window
  *
  *  Adds UTF-8 text to the end of the current text. The newline character starts a
@@ -134,7 +134,7 @@ void SDLTest_TextWindowAddText(SDLTest_TextWindow *textwin, SDL_PRINTF_FORMAT_ST
  */
 void SDLTest_TextWindowAddTextWithLength(SDLTest_TextWindow *textwin, const char *text, size_t len);
 
-/**
+/*
  *  \brief Clear the text in a multi-line text output window
  *
  *  \param textwin The text output window
@@ -143,7 +143,7 @@ void SDLTest_TextWindowAddTextWithLength(SDLTest_TextWindow *textwin, const char
  */
 void SDLTest_TextWindowClear(SDLTest_TextWindow *textwin);
 
-/**
+/*
  *  \brief Free the storage associated with a multi-line text output window
  *
  *  \param textwin The text output window
@@ -152,7 +152,7 @@ void SDLTest_TextWindowClear(SDLTest_TextWindow *textwin);
  */
 void SDLTest_TextWindowDestroy(SDLTest_TextWindow *textwin);
 
-/**
+/*
  *  \brief Cleanup textures used by font drawing functions.
  */
 void SDLTest_CleanupTextDrawing(void);